Train control system



F. H. NICHOLSON 7 2.1603568 TRAIN CONTROL SYSTEM Filed July 8, 1938 May 30, 1939.

- IN NTOR EdHfiH/Vi 0 1 HIS ATTORNEY Patented May 30, 1939 UNITED STATES TRAIN CONTROL SYSTEM Frank H. Nicholson, Penn Township, Allegheny County, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application July s, 1938, Serial No. 218,137

6 Claims.

'My invention'relates to train control systems, and particularly to systems of the type incorporating receiving apparatus usually located on a train and capable of operation either over territory in which the Wayside is supplied with coded current or over'territoryin which the wayside is supplied with non-coded current.

More. particularly my present invention relates to systems inwhich the receiving apparatus is 10 capable of selectively responding to alternating current flowing in the track rails and periodically varied at different rates according to trafiic conditions. A system of this general type is disclosed in United States Patent No. 1,986,679

: grantedto Lloyd V. Lewis on January 1, 1935.

- upon the coded wayside current of the type I disclosed in the Lewis patent identified "above, and which may; for example, be of a frequency of 100 cycles per second, but also-in response to the continuous flow of 'uncoded current of a different frequency such as '140 cycles per second flowing in the track rails. Forthis purpose a modulator is provided for periodically varying'the current supplied by a receiver energized from the wayside.

An important feature of the present invention is the provision in a train'control system of the type disclosed in my previous Patent No. 1,909,709 of means on the train effective when the system i'sto beoperated in response to non-coded current for causing the train carried modulator to periodicallytune and detune (at the frequency of the non-coded wayside current) the circuit through which energy from the receiver is supplied to the train carried traflic control device. In a system of this type the trafiic control device m on-the train is rendered immune to false operations by random current produced in the receiver by stray magnetic fields, shock excitation, or other causes.

I shall describe one form of train control system embodying my invention, and shall then point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic view showing one form of apparatus embodying my invention. This drawing discloses as much of a train control system as is necessary to an understanding "of my invention and'inlcudes a train control re- "ceiver R- of the usual form suitable for picking :up current from the track rails. Energy in- -ducedin'the receiver'R issupplied, through a system is intended to operate. l in the receiver circuit alsotunes that circuit to resonance at the same frequency.

(Cl. 246-r-63) receiver circuitincludingcondenser l, with a filter designated generally by th-ereference character F. The filter F is connected with a train carried traffic control device, here shownas' an electron tube E! which is-coupled by a trans- .6 former T2 to a second electron tube E2. The output circuit of tube E2 controls, by Way of a transformer T3, the winding of a master relay MR which may control train carried governingmeans in any well known manner such, for ex- 10 ample, as shown in the Lewis Patent No. 1,986,679 identified above.

- In the form here shown, the filter F comprises an auto transformer TI connected with the receiver circuit and having its'secondary-terminals 5 connected across the grid and filament of'the train control device El. A condenser3 is permanentlyconnected across the auto transformer Ti and tunes thefilter to resonance at the frequency of the non-coded current with which the F20 The condenser The train carried apparatus also includes a manually operable cutover switch S comprising T25 two contacts 4 and 5 closed in-the'position illustrated which corresponds to operation of the 'in parallel with condenser 3 in the filter F for .30

tuning the filter to resonance at the frequency of the coded current. Similarly whencontacti of switch S is closed a condenser l is connected in parallel with condenser l to tune the receiver circuit to the frequency of the coded current.

With the switch S in the position shown, if the receiver is located'in inductive relation with track rails supplied with coded current, th'e energy induced in the receiver passes through the receiving circuit and'the' filter F to control'the 40 device El and hence the master relay MR.

It is desired however that the system shall also respond when the receiver is in inductive relation with conductors carrying non-coded current. For this purpose the train is provided with a modulator M which may be of the construction disclosed in United States Patent No. 1,858,876, issued May 17, 1932, to 'P. N. Bossart, and comprises a winding 8 which when energized'moves an armature in one direction thereby breaking the operating circuit at contact 9, whereupon a spring restores the armature to again complete the operating circuit at contact 9. Modulator M therefore operates to periodically open and close contacts Ill and II, and the parts are so designed false currents in the receiver.

nected across condenser l of the receiving circuit when contact ll of the modulator is closed. Furthermore I have provided an energizing circuit for the modulator M including contact M of switch S and a suitable source of energy such as a generator G. It is apparent therefore that when the switch S is moved to the position to open contacts 4 and 5, contact l3 will become closed to actuate modulator M.

In operation the switch S will be moved to the position illustrated in the drawing when it is intended that the system shall be used in territory supplied with coded wayside current. Under these circumstances, both the receiver circuit (condensers I and 'l) and the filter (condensers 3 and 6) are tuned to resonance at the frequency of the coded current.

If now it is intended that the system should operate in territory where the wayside is supplied with non-coded current the switch S is moved to the dotted line position thereby rupturing the circuits for condensers 6 and l and causing the receiving circuit and the filter to be tuned to resonance at the frequency of the non-coded current. At the same time the closing of contact l3 of switch S actuates the modulator M and the contacts l0 and l I of the modulator then operate at the code frequency which is to be simulated in the train carried apparatus to alternately connect condensers l2 and I3 in the filter and receiving circuits, respectively, for the purpose of detuning those circuits for the non-coded frequency. The effect of this operation is to periodically vary the impedance offered by the receiving circuit and. the filter to the flow of current from the receiver to the device E l, thereby causing in the current actually supplied to El periodic variations at the rate of operation of modulator M and these period variations in the current supplied to El cause that device to respond and hence to control through the master relay MR and associated apparatus the train carried equipment in exactly the same way as if the receiver were supplied with coded current.

Experience has shown that when the receiver is operating in non-coded territory there may be These false currents may result from the stray field produced by magnetized wheels or from shock excitation due to periodic striking of the receiver by a loose object on the locomotive. It is important that these false currents shall not falsely operate the train carried apparatus. With the apparatus embodying my invention this is prevented because, since the train carried modulator M merely changes the tuning of the receiver circuit and the filter, any false current in the receiver due to the causes suggested above will merely be changed in frequency by the operation of the modulator and will not be substantially changed in amount.

The false current will therefore cont nue to energize device El and the magnitude of the false current will not be periodically varied as is necessary in order to cause operation of the ,master relay MB in accordance with the coded current.

Even under the worst condition, therefore, that is, when shock excitation becomes so frequent that the false currents in receiver R are practically continuous, the operation of the modulator M will merely change the frequency of the false currents supplied to device El and will not materially change the magnitude of this current so that the train carried apparatus is not falsely actuated. When the receiver R is energized by the non-coded current, however, the effect of the modulator is to periodically tune and detune the filter and receiving circuits at this particular frequency and this results in periodic and substantial variations in the magnitude of the current supplied to the device El which causes a consequent operation of the master relay MR.

It will be understood that if the false output from the receiver is of an intermittent character, themaster relay may operate at the frequency of the intermittent excitation of the receiver. Tests have shown however that when this intermittent excitation approaches the periodicity of the code customarily employed for a clear indication per minute) the output of the receiver-filter combination becomes substantially continuous and the master relay remains at rest.

It will be apparent from the foregoing that I have devised a system of train control capable of operation over either coded or non-coded territory and immune to false operation from shock excitation of the receiver.

Although I have herein shown and described only one form of train control system embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims Without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. Ina train control system including a receiver to be energized by modified or unmodified current flowing in a wayside conductor, a traflic control device responsive to the influence of modified current, circuit means for connecting said receiver with said device, a modulator, and means controlled by said modulator for tuning said circuit means alternately and repeatedly to two different frequencies for so modifying the current supplied to said device by the receiver when the latter is energized by unmodified current as to cause response of said device.

2. In a train control system including a receiver to be energized by modified current of one frequency or unmodified current of a second frequency flowing in a wayside conductor, a traffic control device responsive to the influence of modified current, a filter connected with said device and tuned to resonance at said second frequency, a receiver circuit connecting said receiver with said filter and tuned to resonance at said second frequency, a modulator effective when actuated to periodically detune said filter and said receiver circuit for said second frequency, a switch, means controlled by said switch in one position to change the tuning of said filter and receiver circuits to resonance at said one frequency, and means controlled by said switch in a different position to actuate said modulator.

3. In a train control system including a receiver to be energized by unmodified current, a traffic control device responsive to the influence of periodically varied current, circuit means for connecting said receiver with said device, and a modulator for periodically and alternately tuning and detuning said circuit means for the frequency of said unmodified current for causing operation of said device in response to said unmodified current in said receiver but for rendering said device immune to the efi'ects of shock and stray field excitation of said receiver.

4. In a train control system including a receiver to be energized by non-coded periodic current, a trafiic control device responsive to the influence of coded current, circuit means for connecting said receiver with said device, and a modulator for tuning said circuit means alternately and repeatedly to two diiferent frequencies to code the current supplied to said device from said receiver.

5. In a train control system including a receiver to be energized by non-coded periodic current, a trafiic control device responsive to the infiuence of coded current, circuit means for con- 20 necting said receiver with said device, and a modulator for coding the current supplied to said device from said receiver and operating to tune said circuit means alternately and repeatedly to two different frequencies one of which corresponds to the periodicity of said non-coded current.

6. In a train control system including a receiver to be energized by coded alternating current of a first frequency or non-coded alternating current of a second frequency, a trafiic control device responsive to said coded current, circuit means for connecting said receiver with said device, and a modulator for alternately and repeatedly tuning said circuit means to resonance at said first and said second frequencies to code the current supplied to said device from said receiver when the latter is energized by noncoded current.

FRANK H. NICHOLSON. 

